If you run out of space in the root
file system, odd things can happen when you try to map virtual devices to
virtual adapters with mkvdev.

For example, a colleague of mine was
attempting to map a new hdisk to a vhost adapter on a pair of VIOS. The VIOS
was running a recent version of code. He received the following error message
(see below). It wasn’t a very helpful message. At first I thought it was due to
the fact that he had not set the reserve_policy
attribute for the new disk to no_reserve
on both VIOS. Changing the value for that attribute did not help.

I found the
same issue on the second VIOS i.e. a full root file system due to a core file
(from cimserver). I also found no trace of a full file system event in the error
report. Perhaps someone had taken it upon themselves to “clean house” at some
point and had removed entries from the VIOS error log.

Make sure
you monitor file system space on your VIOS. Who knows what else might fail if
you run out of space in a critical file system.